The application of an atmospheric-pressure nitrogen dielectric-barrier discharge to polymer substances is a well-known, cost-effective manner of modifying surface properties of polymer substances. Polymer substance as used herein includes any polymer material, such as films, foams, non-wovens, three-dimensional objects, etc. Atmospheric-pressure nitrogen dielectric-barrier discharge as used herein refers generally to any process in which active nitrogen species (such as free radicals, ions, or electrically or vibrationally excited states) are produced by electron impact with nitrogen-containing molecules.
Atmospheric-pressure nitrogen dielectric-barrier discharge as used herein is also known by many other terms. These terms include but are not limited to nitrogen corona, nitrogen corona discharge, nitrogen barrier discharge, atmospheric-pressure nitrogen plasma, atmospheric-pressure nitrogen glow discharge, atmospheric-pressure nonequilibrium nitrogen plasma, silent nitrogen discharge, atmospheric-pressure partially ionized nitrogen gas, nitrogen filamentary discharge, direct or remote atmospheric-pressure nitrogen discharge, externally sustained or self-sustained atmospheric-pressure nitrogen discharge, and the like.
Modifications achieved by the atmospheric dielectric-barrier discharge include the affixation of nitrogen to the surface of the polymer substance. Wetting properties of the surface are greatly improved, thereby making the polymer substance useful for more applications than if the surface were left untreated.
However, there are shortcomings to the conventional application of an atmospheric-pressure nitrogen dielectric-barrier discharge. For example, the ratio of added nitrogen-to-added oxygen for the surface of the polymer may be lower than desired. Added nitrogen and added oxygen as used in this ratio refer to the atomic nitrogen and atomic oxygen, respectively, that are affixed to the polymer surface specifically by the discharge process. As another shortcoming, the contact angles of water or another liquid on the treated polymer surface may be higher than desired. Additionally, the surface of the polymer may be sensitive to exposure to water or other liquids, whereby water or other liquids reduce the wetting properties of the polymer.